Process for treating an article with a volatile fluid

ABSTRACT

A system for processing a product with a solvent containing volatile constituents, the system including a pressure chamber for receiving the product, a vacuum pump for evacuating the chamber, a solvent recirculating system for admitting the solvent at a predetermined pressure into the chamber, the solvent recirculating system including a heater for maintaining the temperature of the chamber at the saturation temperature of the solvent, gas liquid separator for separating the gas and liquid components of the solvent discharged from the chamber, a first closed loop system connected to the separator to return the gas constituent to the chamber and a second closed loop system connected to the separator to return the liquid component to the chamber.

RELATED APPLICATION

This application is a continuation of co-pending application 07/847,262,filed on Mar. 6, 1992, entitled: A SOLVENT RECOVERY AND RECLAMATIONSYSTEM, now U.S. Pat. No. 5,232,476, issued on Aug. 3, 1993, which is acontinuation-in-part of U.S. application No. 07/581,020, filed on Sep.12, 1990, entitled: EMISSION CONTROL SYSTEM FOR FLUID COMPOSITIONSHAVING VOLATILE CONSTITUENTS AND METHOD THEREOF, now U.S. Pat. No.5,106,404, issued on Apr. 21, 1992, both of which are assigned to thesame Assignee.

FIELD OF THE INVENTION

The present invention relates to solvent cleaning systems wherein boththe gaseous and liquid solvents are separately recycled.

BACKGROUND OF THE INVENTION

In the copending application a solvent vapor emission control system isdisclosed in which the solvent vapor is recycled through a closed loopsystem. This system generally includes a closed chamber in which theprocessing of items is carried out at atmospheric pressure and thus iscapable of use only with cleaning solvents at atmospheric pressure. Thebalance of the system is dedicated to solvent recovery and reclamationfunctions.

SUMMARY OF THE PRESENT INVENTION

The present invention relates to a recovery and reclamation system inwhich a number of related processes are found to be capable of use withminimal modification of a basic vacuum to vacuum, VTV, system. Since theconditions of temperature and pressure within the chamber, once it isisolated from the reclamation and recycling systems, are controllableover wide limits, an entirely new set of operating conditions and, insome cases, new solvents, can be used. The control of the combination oftemperature and pressure allows compounds that are gases at roomtemperature to be liquefied, e.g., HCFC-22 (refrigerant 22) and DME(dimethyl ether), to be used as solvents. Conversely, compounds that areliquids under room conditions can be made to boil at selectedtemperatures by reducing chamber pressure. Thus, conventional treatmentprocesses, including ultrasonic cleaning (U/S), flushing, low and highpressure sprays and recirculating sprays, immersion; boiling immersion;and spray over immersion; can be used with present solvents as well ascompounds not practical in present equipment systems.

One of the primary benefits of the present system includes very lowsolvent emission generally related to either nonreducible solventadsorption by the item being cleaned and/or from still bottoms generatedin the solvent recycling step. Good maintenance is required to avoidleaks, both of air in and solvent out. High initial and final vacuumsare important in reaching the full potential of the VTV solvent emissionreduction capability. While there are benefits from using any level ofvacuum, the higher the initial and final vacuum, the better. Practicalvacuums of 29 inches mercury column or higher are achievable andrecommended.

Other principal features and advantages of the invention will becomeapparent to those skilled in the art upon review of the followingdrawings, the detailed description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the basic VTV system.

FIG. 2 is a schematic diagram for a defluxing/cleaning system using asolvent recycling system.

FIG. 3 is a schematic view of a maintenance cleaning system using twosolvents.

FIG. 4 is a schematic view of a dry cleaning system for launderingclothes.

FIG. 5 is a schematic side view of the dry cleaning system of FIG. 4.

FIG. 6 is a schematic view of an alternate form of dry cleaning system.

FIG. 7 is a schematic view of displacement and drying system for waterremoval from metal, plastic or glass.

Before explaining at least one embodiment of the invention in detail itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments or being practiced or carriedout in various ways. Also, it is to be understood that the phraseologyand terminology employed herein is for the purpose of description andshould not be regarded as limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the major components of the recovery andreclamation closed loop system 10 generally include a vacuum chamber 12which is connected to a vacuum pump 18 through pipe or tube 32, valve113 and tube 20 to remove the gaseous contents of chamber 12 or directlyto gas/liquid separator 34 through valve 111 in tube 33. Valves 23 and24 are connected to the pump 18 through tube 22 to isolate the chamber12 and enable the discharge from the vacuum pump 18 to be selectivelydischarged to atmosphere through valve 24 in tube 26 or to the closedloop system through valve 23 in tube 28 to tube 25. The gas chamber 38of receiver 34 is connected to a low pressure accumulator 54 throughtube 25 and valve 52. The solvent liquid in liquid receiver 36 isdischarged to a solvent reclamation reservoir 48 through valve 45 intube 46. Gas in accumulator 54 is released by instrumentation 58 to agas compressor 60 through tube 56. Pressurized gas passes through tube64 to compressor after cooler 66 which is connected to stripper 68 bytube 64. A chiller 74 is connected to heat exchanger 72 by tubes 76 and78 to maintain a low temperature in heat exchanger 72. Condensed,recovered solvent from stripper 68 is returned to the liquid receiver 36through tube 80, valve 82 and tube 84. High pressure gas from stripper68 passes through tube 86 to receiver 88. High pressure gas may bevented through pressure reducing valve 102 to atmosphere or to a carbonadsorber. Gas from receiver 88 passes through tube 92 and pressurereducing valve 94 to a gas heater 96 and control valve 14. The gas isheated in gas heater 96 by a heat exchanger 100 connected to a heatsource 98. Solvent from recovery system 48 or solvent gas from heater 96can be selectively admitted to chamber 12 by means of control valve 14.

The present invention uses the above recovery and reclamation system ina number of related processes as described herein. Only minimalmodification is necessary to accommodate the physical characteristics ofthe various solvents or treatment processes.

The basic VTV (vacuum to vacuum) system as described above operates asfollows. An item to be processed is placed in chamber 12. The chamber issealed. Chamber 12 is isolated from the rest of the system by solenoidvalves 188, 190, 101, 103, 111 and 113. Valves 113 and 24 are opened andvacuum pump 18 is activated. The gaseous contents of the chamber arewithdrawn and discharged via port 26, either to atmosphere or to arecovery means such as a carbon adsorber or solvent vapor incinerator.Once the air in chamber 12 has been removed, valves 113 and 24 areclosed and the vacuum pump 18 is turned off. Valve 101 is opened to gasliquid separator 34 to break the vacuum in the chamber with gas,containing some fraction of solvent vapor, from within the closed loopsystem 10. An alternative method to break the vacuum is to admit liquidsolvent via valve 188 into chamber 12. The admitted liquid will flash tovapor, filling chamber 12 with solvent vapor with only a small fractionof noncondensable gas in it. The benefit of the latter process will beseen below.

Solvent for processing is supplied, under pressure from solvent supplysystem 48. The solvent supply system can take many forms depending onthe solvent used and process requirements. Its function is to receiveused solvent and to supply fresh solvent of required purity at therequired pressure and volume. It may or may not recycle (purify) theused solvent. Solvent under pressure is admitted to chamber 12 byopening valve 188. The solvent is flushed over the item to be treated inchamber 12 and is drained to the liquid/gas separator 34 through valve111. Liquid flows by gravity to liquid receiver 36 while solvent vaporor gas rises into gas well 38. When liquid receiver 36 is full,instrumentation 42 opens valve 45. Pump 44 returns liquid solvent to thesolvent supply system 48 where it may be processed for reuse.

When instrumentation 50 senses pressure in gas well 38, valve 52 isopened, admitting gas to low pressure gas accumulator 54. Compressor 60starts. The discharge from compressor 60 is cooled by intercooler 66before it enters stripper 68. Most of the solvent vapor enteringstripper 68 is condensed into liquid form on the cold surface of heatexchanger 72 which, in turn, is kept at low temperature by chiller 74.The stripped, or solvent dehumidified gas leaving stripper 68accumulates in high pressure gas receiver 88.

At the end of the cycle, most of the gas in the system has beencompressed and stored in high pressure accumulator 88. Any excesspressure above set point of pressure relieving valve 102, due toingested air and the resultant increase effect thereof on maximum systempressure, is vented through valve 102 to atmosphere or through a carbonadsorber or solvent incinerator (not shown).

The process steps are as follows:

1) Gases are evacuated from chamber 12 and discharged to atmosphere.

2) The item to be treated is exposed to solvent through valve 188.

3) Dry air from the closed loop system is blown through valve 190through chamber 12 to remove as much solvent in liquid form as possible.

4) Heated dry air is circulated through chamber 12 to warm and evaporatethe remaining solvent.

5) Chamber 12 is evacuated and its contents discharged within theclosed, solvent recovery loop 10. An intermediate vacuum step to improvedrying may be bypassed in some processes where a single evacuation willsuffice.

6) Chamber 12 is evacuated by vacuum pump 18 and discharged within theclosed, solvent recovery loop.

During the purging and drying steps, air from high pressure receiver 88is conducted through pressure control valve 94 into air heater 96,through valve 190 into chamber 12. The gas circulates sequentially inthe closed loop from chamber 12 to gas/liquid separator 34, compressor60, stripper 68, heater 96 and back to chamber 12 for as long as theprocess requires.

After the drying step is complete, chamber 12 is isolated once again byclosing valves 188, 190, 101, 103, 111 and 113. Valves 113 and 23 arethen opened and vacuum pump 18 is started. The contents of chamber 12are evacuated and, since the gas contains solvent vapor, are dischargedwithin the closed loop system.

The vacuum in chamber 12 is broken with room air by opening valve 103.Chamber 12 may then be opened and the processed item removed. At anappropriate time in the cycle, valve 82 is opened to allow recovered,condensed liquid solvent in stripper 68 to flow through tube 80 toliquid receiver 36.

In the following processes various applications of the closed loopvacuum-to-vacuum process are described wherein the recovery andreclamation closed loop system will remain as described above.

Printed Wiring Assembly Defluxing/Cleaning

Performance and reliability of printed wiring assemblies depends on thelevel of cleanliness achieved. While no-clean, water and semi-aqueousprocesses are adequate for many printed wiring assemblies, the moreadvanced assemblies, with close conductor spacing, require highercleanliness. Solvents such as CFC-113, methyl chloroform, as well asflammable solvents such as methyl, ethyl or isopropyl alcohol orhydrocarbons, may be used. Chlorodifluoromethane (a/k/a R-22) has beenchosen for purposes of exemplifying the capabilities of the system. Theterm "S-22" is used to indicate the use of chlorodifluoromethane as asolvent.

A defluxing process using the S-22 solvent for cleaning printed wiringassemblies as described herein includes flushing or spraying theassemblies, followed by a recirculation flush or spray if needed and afresh solvent rinse. Immersion with or without ultrasonic (U/S)agitation followed by flush or spray or other processes can also be usedto clean the assemblies.

Referring to FIG. 2, a system is shown for solvent cleaning of one ormore printed wiring assemblies 100 with a solvent that is gaseous atroom conditions. The chamber 12 is shown with a number of printed wiringassemblies 100 placed in a spaced relation in basket 104. A solventsupply system 105 is connected to the gas liquid separator 34, through atube 106 and a valve 47. The liquid flows through tube 106, valve 47 andport 110 into the solvent supply system 109. The purpose of the solventsupply system 109 is to maintain a supply of fresh, liquid solvent tosolvent reservoir 108 according to the overall needs of the process. Apump 112 is used to draw liquid from receiver 108 through a tube 114which is connected to pressure relief valve 116. Pressure in tube 114 inexcess of set point of pressure relief valve 116 is vented back to theliquid receiver 108 through line 118. The liquid S-22 is thus maintainedat a constant, preset pressure at valve 116.

In order to achieve the proper temperature and pressure for thisprocess, a solvent heat exchanger 120 is provided in tube 114. The heatexchanger 120 is heated from a heat source 122. The wall temperature ofchamber 12 is controlled by heaters 124 and 126.

To clean the printed wiring assemblies 100, the chamber 12 is sealed andevacuated by vacuum pump 18 through valve 113 in line 20. Since pressureis required in chamber 12 when using S-22 in liquid form, the vacuum inchamber 12 is broken with liquid solvent by opening valve 188. LiquidS-22, under pressure generated in the solvent supply system 105, isadmitted to chamber 12 through valve 188. After the vacuum in chamber 12is broken, solvent continues to enter the chamber through valve 188,until the pressure reaches the saturation pressure of the S-22 for thetemperature in chamber 12. Liquid S-22 entering chamber 12 will notflash to vapor but will remain liquid. In order to achieve the describedcombination of temperature and pressure for this step in chamber 12, thesolvent may be heated in heat exchanger 120. The temperature within thechamber 12 is controlled by heaters 124 and 126. After the treatmentprocess has been completed, valves 111 and 47 are opened to conductliquid solvent from the chamber to the solvent supply system 109 throughtube 32, valve 111, separator 34, tube 106, valve 47 and port 110. Whenall liquid has been recovered valve 47 is closed. Pressure in thechamber 12 is then reduced to approximately room pressure. Valve 190 isopened and gas in closed loop 10 is circulated, as described in FIG. 1,to dry the parts and recover solvent in the stripper 68. Recoveredliquid in stripper 68 is returned to solvent supply system 109 by pump140 through check valve 142 and tube 144 to port 110. The pressure isrelieved by opening valve 111 to gas liquid separator 34. Any solventgas is reclaimed through the closed loop system 10 as shown in FIG. 1.

The pump 112 draws liquid S-22 from receiver 108 and is supplied topressure accumulator 65. If the pressure in tube 114 downstream frompump 112 exceeds the set point of pressure relieving valve 116, theliquid is vented back to the receiver 108.

For flushing or spraying processes, solvent S-22 is passed through spraynozzles 128 strategically positioned relative to the printed wiringassemblies 100. When using S-22, the chamber 12, gas liquid separator 34and solvent reclamation system 105 must be built to contain the pressureof S-22 at process temperatures. That pressure would be 121, 168 or 260psig at 70°, 90° or 120° F., respectively.

For a recirculating spray followed by fresh rinse, solvent is admittedthrough valve 188 and the spray heads 128 until a preset volume ofliquid S-22 accumulates in the well 130 at the bottom of chamber 12.Valve 188 is closed and pump 132 in line 134 circulates liquid S-22through one-way valve 136 back to the spray nozzles 128 in chamber 12.Recirculation is continued as long as required.

If an ultrasonic process is used, chamber 12 is provided with ultrasonicvibrators 140 on the walls of chamber 12. The chamber 12 is filled withliquid S-22 to a level above the printed wiring assemblies 100. Thecontrol of temperature and pressure for the ultrasonic process is morecritical than for other processes. Assuming a given, controlledtemperature, pressure may be varied to control the degree of cavitation,thus the severity of the cleaning action of a constant ultrasonicsignal. Following the ultrasonic step, chamber 12 is drained throughvalve 111 to liquid separator 34. It should be noted that the apparatusdescribed will reduce solvent emissions from currently practiced printedwiring assembly cleaning processes. A wider range of solvents may beused since the system is no longer restricted to an atmospheric pressuretreatment vessel.

Maintenance Cleaning

Referring to FIG. 3, a system is shown for using more than one treatmentfluid in the cleaning process. In the case of an electromechanicaldevice such as a typewriter, mechanical clock, or mechanical printer,these devices require periodic cleaning and relubrication to maintainconsistent performance. In this type of a cleaning process, chamber 12is provided with a number of spray nozzles 141 mounted on a manifold 147at the top of the chamber 12. The mechanical device 149 is placed in thechamber and is initially cleaned with a solvent as described above.After cleaning and drying is complete, a solvent/lubricant solution ispumped from a receiver 145 by a pump 132 through line 134 and checkvalve 136. A spray manifold 143, separate from the cleaning spraymanifold 147, is used to direct the solvent/lubricant solution to thedesired locations of the item to be cleaned. In some instances, it maybe necessary to fill the chamber 12 to allow the solvent/lubricant toflow into the interstices of mechanical device 149. Thesolvent/lubricant solution is then drained back to receiver 145 throughvalve 146 in line 135. A final rinse to cleanse the exterior surface ofthe lubricant may be used. The nodal drying and final evacuation stepsfollow. Lubricant is carried into the bearing surfaces and left there asthe carrier solvent is evaporated in the drying steps.

Lubricants are available that are insoluble in common solvents. Thesemay be used to prevent removal during the cleaning step.

Clothes Dry Cleaning

Referring to FIGS. 4 and 5 a system is shown for laundering or drycleaning clothes. The chamber 12 as shown includes a rotary tub 160mounted on shaft 162 in chamber 12. The tube 160 is supported bybearings 164 and rotated by drive mechanism 166. The drive mechanism maybe any conventional motor, gear motor, hydraulic motor, etc. for turningthe tub 160 at a desired speed for washing and drying and at a higherspeed for centrifugal extraction. The top of chamber 12 is provided witha liquid distributor spray system 165 to distribute solvent through theperforations 170 in the outer surface of the tub 160. Chamber 12includes a drain 172 which is in fluid communication with a circulatingpump 174 which draws solvent from the bottom of chamber 12 andrecirculates it through check valve 176 to spray system 165. Heatexchangers 178 and heat source 180 control the temperature of theentering solvent and thus control pressure in chamber 12. Spacer blocks182 and 184 are used to reduce the interior volume of chamber 12, thuscontrolling the charge of liquid in chamber 12.

In operation the door 186 is opened and the clothes to be treated areplaced in tub 160. Door 186 is closed and sealed, as described above.Chamber 12 is evacuated and its contents discharged to atmosphere.Vacuum in tub 160 is broken by opening solenoid valve 188 to allowsolvent to enter the chamber. The temperature of incoming solvent iscontrolled by heat exchanger 178. Maintaining solvent temperature suchthat the chamber pressure is close to ambient will reduce the effect ofany leaks although solvents that are gaseous at room conditions may beused as described in FIG. 2 above. Drive system 166 turns tub 160,tumbling the clothes. Chamber 12 is allowed to fill with liquid to thedesired level. Pump 174 recirculates the charge of solvents during thewashing step. After washing the solvent charge is drained through valve111 to the gas liquid separator 34. A clean solvent rinse may be used.

Drive system 166 then turns tub 160 at a higher speed to centrifugallyextract as much liquid solvent as possible. Valves 111 and 52 remainopen during the drying step.

Valve 190 opens admitting warm dry solvent dehumidified air from theclosed loop system 10 to chamber 12. The air passes through tub 160 andthe tumbling clothes. The heat provides energy to evaporate theremaining liquid solvent. Solvent vapor is carried by the air in theclosed loop 10 to the stripper 68 for condensation and reclamation asdescribed above.

After the liquid solvent has been evaporated and the clothes are dry,chamber 12 is once again isolated from the rest of closed loop 10 byclosing valves 188, 190, 111, 103 and 101. Valves 113 and 23 are openedand chamber 12 is evacuated by vacuum pump 18, FIG. 1, dischargingthrough valves 23 into tube 25 in closed loop system 10. Vacuum in thechamber 12 is broken by admitting air through valve 103. The chamber 12may then be opened to remove the cleaned clothes.

Closed Loop Variation For VTV

The solvent emissions control system as shown in FIG. 6 is a variationof the base system, FIG. 1. Pressure blower 192 replaces compressor 60and after cooler 66. The blower may be a regenerative blower, with shaftseal, of the EG&G Rotron Degenerative Blower Model DR-404 type. Theblower 192 provides the pressure needed to recirculate air through a gasexiting heater 96, chamber 12, gas liquid separator 38 and stripper 68which is placed downstream of heater 96 to more effectively circulateair in the system. Gas entering stripper 68 is of higher volume than gasexiting heater 96. The amount of air circulating is nearly constant,however the gas volume leaving chamber 12 has been augmented by solventvapor picked up in the cleaning process within chamber 12. Most of thesolvent is condensed in stripper 68, leaving only air with a smallfraction of solvent vapor going on to blower 192. The higher gas flowrates speed drying.

The volume of gas within the system will vary depending on the amount ofsolvent vapor present. An accumulator 200 in the form of a bladder orslack sided accumulator allows containment of the extra volume withoutincreased system pressure. Instrumentation 201 such as a light beam orcontact device senses bladder 200 size. When the upper limit of bladder200 size is reached valve 202 is opened for a predetermined time ventinggas from the system. The gas vented through valve 202 contains thelowest concentration of solvent in the system, therefore minimizingsolvent loss due to air ingestion and subsequent venting of that air.

As before, after drying is complete chamber 12 is sealed by closingvalves 101, 103, 111, 113, 188 and 190. Valve 113 is opened and vacuumpump 18 evacuates chamber 12 discharging air/solvent vapor mixturethrough valve 23 to tube 25 in the closed loop system 10. It ismentioned above that several intermediate vacuums followed by heated aircirculation enhances the speed and completeness of the solvent removal.

A variety of solvent handling strategies to enhance cleaning on one handand reduce solvent reclamation volume on the other hand may be used. Onemay treat the solvent with a filter adsorber or distiller for each batchof clothes to get the ultimate in cleanliness. The basic charge for thewashing step may be retained so that it can be used over until its soilcontent reaches some limit. The washing charge may be diluted in eachcycle with a rinse charge to maintain soil level in the washing chargeat some more or less constant.

Displacement Drying

Water removal from a metal, plastic or glass component following a waterprocess poses several problems. Evaporative drying both uses significantamounts of energy and leaves a residue from water droplets deposited onthe surface of the item. Water displacement, i.e. the floating of waterdroplets from the surface and water adsorption processes have beencommercialized by others.

Displacement processes use alcohol adsorption or FREON™ T-DFC solvent, aCFC-113 base solvent/detergent mixture, to displace water and remove itfrom the surface of the item being dried. The detergent then is removedby a solvent cleaning step. The cleaning solvent evaporates spot-free.In the adsorption process an alcohol such as methyl, ethyl or isopropylalcohol which has the capacity to adsorb water, up to the saturationlimit of the alcohol, is flushed over the part to be dried. Most often anonflammable solvent such as CFC-113 is used in combination with thealcohol to keep the resultant mixture nonflammable.

Referring to FIG. 7 a displacement drying system using two solventsolutions is shown. In this system gas/liquid separator 34 is connectedto two liquid supply systems, one for the solvent/detergent solution 204and the other for the clean solvent 206.

Product is introduced into chamber 12 using the vacuum steps describedabove. During the dewatering step solvent-detergent solution is drawnfrom reservoir 202b by pump 204b and enters chamber 12 through tube 43band valve 30b. Water is displaced and is carried from chamber 12 withthe solution. Liquid solution is returned to solvent supply system 48bthrough valve 33b and pump 44b. Solvent supply system 48b providessolution of proper composition to reservoir 202b through check valve200b. Vaporized solvent is recovered in closed loop 10 as describedabove. That solvent is distilled solvent free of detergent and may bereturned to the solvent reservoir 202a through valve 33a, pump 44a,supply system 48a and check valve 200b.

After all liquid solution has been drained from gas-liquid separator 34the part is flushed by admitting fresh solvent from reservoir 202a viapump 204a, tube 43a and valve 30a into chamber 12. Solvent liquid isreturned to the solvent supply system where the detergent is removed andthe solvent is purified to the extent required.

After the dewatering and detergent removal steps the item beingprocessed is dried and removed by the evacuation process describedabove.

Cross contamination of detergent into cleaning solvent may be reduced byproviding a short rinse of clean solvent from tank 202b through valve30b and diverting the rinse effluent into the drying agent tank 202a.The option of directing recovered solvent from stripper 68 through valve82 to either the drying agent tank 202a or the solvent tank 202b isbased on the contamination level of detergent in the return solvent.

Thus, it should be apparent that there has been provided in accordancewith the present invention a solvent recovery and reclamation systemthat fully satisfies the objectives and advantages set forth above.Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A process for treating an article with a volatile fluid, which comprises:(a) disposing the article in a chamber in a manner that admits air to the chamber; (b) sealing the chamber; (c) evacuating the chamber to remove substantially all of the air therefrom; (d) introducing the fluid into the chamber so that the fluid contacts the article and fills the chamber with fluid vapors; (e) evacuating the chamber to remove fluid vapors therefrom; (f) drying the article by circulating a gas through the chamber; (g) then evacuating the chamber to remove residual fluid vapors therefrom; and (h) then opening the chamber and removing the treated article from the chamber.
 2. The process of claim 1, further comprising repeating (e) and (f) one or more times prior to final evacuation (g).
 3. The process of claim 1, wherein the gas circulated in (f) is resident in a closed loop including the chamber, further comprising condensing fluid vapor from the gas in a stripper, the gas containing fluid vapor being circulated from the chamber to the stripper and back to the chamber again.
 4. The process of claim 3, wherein the gas consists essentially of air retained within the closed loop, further comprising a step of relieving pressure within the closed loop due to air build-up caused by residual air present in the chamber after (c).
 5. The process of claim 3, further comprising heating the gas prior to circulating it through the chamber by passing the gas through a heater provided in the closed loop disposed downstream from the stripper.
 6. The process of claim 5, further comprising compressing the gas, prior to condensing fluid vapor therefrom in the stripper, in a compressor provided in the closed loop upstream from the stripper between the chamber and the stripper.
 7. The process of claim 1, further comprising heating the gas prior to circulating it through the chamber.
 8. The process of claim 1, further comprising a step of filling the evacuated chamber with air prior to opening the chamber and removing the article therefrom in (h). 